A three dollar word for rust, and also the material that makes up the business side of recording tape. When metal “oxidizes” (rusts) its chemical/electrical properties change (the actual chemistry lesson is beyond the scope of what we need here), and in some metals becomes suitable for use in recording tape. There are many different tape formulations that are based on different kinds of oxidized metals (chromium, for example), and varying degrees of oxidation, but the bottom line is that, for all practical purposes, we are recording on rust! This oxide material is affixed to some sort of backing (the tape) that can be placed on reels (for recording), platters (for disks), or plastic (for credit cards). This oxide is also the material that sheds from recording tape and accumulates around your tape transport components. It looks like little brown flakes. The more oxide that is shed, the less effective your recording tape becomes.